Abstract

Abstract

Aluminum toxicity is a deterrant to the growth of plants in acid soil. Little is known of the initial site or sites of A1 injury in plant roots nor of the sequence of events that characterize A1 toxicity. The objective of this study was to document some effects of short-term exposure to Al in two wheat (Triticum aestivum L.) cultivars, Eagle and Atlas 66. Root elongation in Eagle was much more susceptible to concentrations of 0.02 to 1.85 mM Al than was root elongation in Atlas 66. A 2-h exposure to 0.19 mM Al drastically inhibited root elongation in Eagle, whereas a 48-h treatment with 0.19 mM Al had little effect on root elongation in Atlas 66. Exposures of Eagle seedlings to 0.19 mM Al for 4 h caused a 32% inhibition in subsequent incorporation of 3H-thymidine into DNA, with the degree of inhibition increasing with duration of exposure to Al. In Atlas 66, there was a 101 reduction in incorporation of radioactivity into the DNA fraction for all the Al pretreatments, ranging from 2 to 48 h. Exposure of Eagle roots to AI for 2 h showed this same 10% reduction in incorporation of radioactivity into DNA. For both cultivars, there usually was a 10 to 20% decrease in 3H-thymidine uptake by whole roots after 0.19 mM Al pretreatment periods of 2 to 12 has compared with control plants not receiving AI. The extent of inhibition was fairly constant and was not correlated with duration of Al pretreatment for either cultivar. There was a similar depression of 3H-thymidine uptake in root tips of Eagle after 4 to 12 h of Al pretreatment. The reduction of 3H-thymidine uptake in both cultivars resembled the depression of 3H-thymidine incorporation into DNA in Atlas 66 but not in Eagle. This work suggests that Al has two effects on susceptible cultivars: a rapid inhibition of root elongation followed by an inhibition of DNA synthesis. Another effect of AI on both the tolerant and the susceptible cultivar, that of depression of 3H-thymidine uptake, also was seen.

Please view the pdf by using the Full Text (PDF) link under 'View' to the left.